1. Field of the Invention
The present invention relates to a method for uniformly forming a thin film on a substrate surface having asperities thereon and further relates to a device used for the method.
2. Description of the Background Art
In general, in manufacturing processes of semiconductor wafers, photolithography technology is used for forming resist patterns on surfaces of substrates (substrates to be processed) such as semiconductor wafers or LCD substrates. This photolithography technology includes a resist-applying step for applying a resist solution to a surface of a substrate to be processed, an exposure treatment step for exposing the resulting resist film to a circuit pattern, and a development treatment step for supplying a developing solution to the substrate after the exposure treatment step. In such a case, the resist-applying step employs a so-called spin-coating method, namely, placing a substrate on a rotatable mounting platform so that the upward-facing surface of the substrate is the face (surface) to be processed, and supplying (dropping or discharging) a resist solution to the surface of the substrate while rotating the substrate. A film of the resist solution is formed on the surface of the substrate by centrifugal force.
In addition, as the related art, electrostatic coating utilizing the principle of electrospray is known (see, for example, Japanese Patent Laying-Open No. 2001-286814).
However, since a resist film is formed on a substrate surface by centrifugal force in the spin-coating method, the resist film tends to have a thickness increasing toward the periphery of the substrate. Therefore, uniformity in the film thickness of the substrate surface is lost. If nonuniformity occurs in the film thickness, later processes are disadvantageously influenced. For example, in an etching process, depth of etching differs depending on the area of the surface. Thus, various problems arise.